linux-kernel - Re: [PATCH v1 0/9] PM: Check power.needs_force_resume in pm_runtime_force

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Message-ID: <CAPDyKForsegoD+J6rumvnhHna7W+DVdb5zdKGiRB-TFv27sy7A@mail.gmail.com>
Date: Thu, 26 Jun 2025 12:10:08 +0200
From: Ulf Hansson <ulf.hansson@...aro.org>
To: "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc: Linux PM <linux-pm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, 
	Linux ACPI <linux-acpi@...r.kernel.org>, Linux PCI <linux-pci@...r.kernel.org>, 
	Mika Westerberg <mika.westerberg@...ux.intel.com>
Subject: Re: [PATCH v1 0/9] PM: Check power.needs_force_resume in pm_runtime_force_suspend()

On Wed, 25 Jun 2025 at 21:25, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> Add a power.needs_force_resume check to pm_runtime_force_suspend() so
> it need not rely on the runtime PM status of the device when deciding
> whether or not to return early.
>
> With the new check in place, pm_runtime_force_suspend() will also skip
> devices with the runtime PM status equal to RPM_ACTIVE if they have
> power.needs_force_resume set, so it won't need to change the RPM
> status of the device to RPM_SUSPENDED in addition to setting
> power.needs_force_resume in the case when pm_runtime_need_not_resume()
> return false.
>
> This allows the runtime PM status update to be removed from
> pm_runtime_force_resume(), so the runtime PM status remains unchanged
> between the pm_runtime_force_suspend() and pm_runtime_force_resume()
> calls.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
>  drivers/base/power/runtime.c |   21 ++++++++-------------
>  1 file changed, 8 insertions(+), 13 deletions(-)
>
> --- a/drivers/base/power/runtime.c
> +++ b/drivers/base/power/runtime.c
> @@ -1975,7 +1975,7 @@
>         int ret;
>
>         pm_runtime_disable(dev);
> -       if (pm_runtime_status_suspended(dev))
> +       if (pm_runtime_status_suspended(dev) || dev->power.needs_force_resume)
>                 return 0;
>
>         callback = RPM_GET_CALLBACK(dev, runtime_suspend);
> @@ -1990,15 +1990,16 @@
>         /*
>          * If the device can stay in suspend after the system-wide transition
>          * to the working state that will follow, drop the children counter of
> -        * its parent, but set its status to RPM_SUSPENDED anyway in case this
> -        * function will be called again for it in the meantime.
> +        * its parent and the usage counters of its suppliers.  Otherwise, set
> +        * power.needs_force_resume to let pm_runtime_force_resume() know that
> +        * the device needs to be taken care of and to prevent this function
> +        * from handling the device again in case the device is passed to it
> +        * once more subsequently.
>          */
> -       if (pm_runtime_need_not_resume(dev)) {
> +       if (pm_runtime_need_not_resume(dev))
>                 pm_runtime_set_suspended(dev);
> -       } else {
> -               __update_runtime_status(dev, RPM_SUSPENDED);
> +       else
>                 dev->power.needs_force_resume = true;
> -       }
>
>         return 0;
>
> @@ -2029,12 +2030,6 @@
>         if (!dev->power.needs_force_resume)
>                 goto out;
>
> -       /*
> -        * The value of the parent's children counter is correct already, so
> -        * just update the status of the device.
> -        */
> -       __update_runtime_status(dev, RPM_ACTIVE);
> -
>         callback = RPM_GET_CALLBACK(dev, runtime_resume);
>
>         dev_pm_disable_wake_irq_check(dev, false);
>

As I mentioned for patch4, pm_runtime_force_suspend() is being used
from driver's ->remove() callback too.

If such a driver/device gets probed again, we need a fresh start. It
seems like we need to clear the needs_force_resume flag in
pm_runtime_reinit(). In fact, that looks like an existing bug, even
before $subject patch, right?

Kind regards
Uffe